The challenge to meet the ever increasing demand for oil includes increasing crude oil recovery from heavy oil reservoirs. This challenge has resulted in expanding efforts to develop alternative cost efficient oil recovery processes (Kianipey, S. A. and Donaldson, E. C. 61st Annual Technical Conference and Exhibition, New Orleans, La., USA, Oct. 5-8, 1986). Heavy hydrocarbons in the form of petroleum deposits and oil reservoirs are distributed worldwide. These oil reservoirs are measured in the hundreds of billions of recoverable barrels. Because heavy crude oil has a relatively high viscosity, it is essentially immobile and cannot be easily recovered by conventional primary and secondary means.
Microbial Enhanced Oil Recovery (MEOR) is a methodology for increasing oil recovery by the action of microorganisms (Brown, L. R., Vadie, A. A,. Stephen, O. J. SPE 59306, SPE/DOE Improved Oil Recovery Symposium, Oklahoma, Apr. 3-5, 2000). MEOR research and development is an ongoing effort directed at discovering techniques to use microorganisms to modify crude oil properties to benefit oil recovery (Sunde. E., Beeder, J., Nilsen, R. K. Torsvik, T., SPE 24204, SPE/DOE 8th Symposium on enhanced Oil Recovery, Tulsa, Okla., USA, Apr. 22-24, 1992).
Methods for identifying microorganisms useful in MEOR processes have been described. These methods require identification of samples drawn from an oil well or reservoir comprising a consortium of microorganisms and enrichment or evolution of populations in the sample under specific conditions with a defined nutrient medium (U.S. Patent Application No. 2007/0092930A1). Thus, there is a need for developing methods to: 1) identify microorganisms that can grow in or on oil under anaerobic denitrifying conditions by selection of pure isolates from enrichment of indigenous microorganisms; 2) screen isolates for properties that might be useful in oil modification or interactions and 3) use said identified microorganisms, in a cost-efficient way, to improve oil recovery.
The organism LH4:18, described herein, was identified by 16S rDNA homology as a strain of Shewanella putrefaciens. The 16S rDNA sequence has 100% homology to two of the eight rDNA genes in Shewanella putrefaciens strain CN32 and W3-18-1. Both Shewanella putrefaciens CN32 (Genome Analysis and System Modeling Group of the Life Sciences Division of Oak Ridge National Laboratory) and S. putrefaciens W3-18-1 (DOE Joint Genome Institute) were isolated from environmental samples and have been studied extensively for bioremediation of heavy metals. Strain Conn.32 has been studied by DOE Natural and Accelerated Bioremediation Research group for its ability to reduce polyvalent metals, including iron, manganese, uranium, and chromium (William D. Burgos, W. D., et al., Environ. Eng. Sci., 24, 755-761, 2007; and Liu, C., et al., Biotechnol. Bioeng. 80, 637-649, 2002). Strain W3-18-1 has been studied for remediation of metals and radioactive materials, especially in cold climates (Stapleton Jr., R. D., et al., Aquat. Microb. Ecol. 38:81-91, 2005). Both strains have utility in decreasing solubility of the metals and stabilizing them in situ.
Many Shewanella putrefaciens can reduce metal oxides, but there are subtle differences in the ability of each strain implying genetic variability beyond the 16S rDNA homologies. Shewanella species are disclosed for remediation of metal contamination (U.S. Pat. No. 6,923,914B2), iron containing mixed waste (U.S. Pat. No. 6,719,902B1), manganese contamination (U.S. Pat. No. 6,350,605B1), and other pollutants with the aide of butane (U.S. Pat. No. 6,245,235B1). In W000/56668 Shewanella species that can utilize butane have been claimed in a method of bioremediation of petroleum contaminants aerobically. In addition, Shewanella supplemented with butane was used for reduction of fouling in injection and recovery wells under aerobic conditions (U.S. Pat. No. 6,244,346B1). Shewanella putrefaciens is known to produce biofilms (D. Bagge, et al., Appl. Environ. Microbiol., 67, 2319-2325. 2001). Biofilms of Shewanella species have potential to sequester gases, in particular CO2, in underground geological formations and prevent their release into the atmosphere (see US20060216811A1). There has been no report to date of Shewanella species utilized in enhanced oil recovery.